Within the heavy-duty trailer design and manufacturing industry, it is desired that a trailer have maximum load carrying capacity and strength/durability. These trailers, such as dump trailers, tipper trailers, walking floor trailers, and others (referred to generally herein as bulk commodity trailers), traditionally have been produced in various lengths and capacities. The trailers generally include a trailer body that defines a cargo-retaining space supported on a chassis. Ground-engaging wheel assemblies are connected to the chassis and movably support the chassis and trailer body on the ground. A retractable landing gear assembly is connected to the chassis or trailer body at a location spaced from the wheel assemblies to support the front of the trailer chassis on the ground when it is not supported by a tractor vehicle used to pull the trailer.
The trailer body, itself, comprises a floor structure. Left and right sidewalls and front and rear walls project vertically upward relative to the floor and, together with the floor, define cargo-retaining space for bulk commodities such as sand, grain, garbage, coal, scrap metal, etc. The rear wall provides or includes or defines a gate that selectively blocks and opens a payload discharge opening.
The top of bulk commodity trailer bodies is typically left open, but a “center-pipe” is often located near the longitudinal midpoint of the trailer body and extends transversely between and interconnects the upper edges of the left and right sidewalls. This center-pipe is used to add strength to the trailer body and, specifically, to prevent outward bowing of the left and red sidewalls due to the weight of the load in the cargo-retaining space. This center-pipe has been found to be inconvenient in that it obstruct the open top of the trailer which impedes loading and can prevent full loading, it can inhibit the dumping of the payload from the cargo-retaining area, and if the center-pipe is accidentally contacted and damaged during loading operations, it can transfer this force to the trailer sidewalls and cause damage thereto.
The trailer body is often pivotally mounted to the chassis and, in such case, the trailer comprises a hydraulic actuator or the like for pivoting the body relative to the chassis for dumping the cargo from the cargo-retaining space through the open rear gate. In other “frameless dump” trailer arrangements, the trailer includes a more limited chassis, and dumping is carried out by pivoting the trailer body and portions of the chassis about a rear set of ground-engaging wheels as is well-known in the art. Other trailer bodies have a live or “walking” floor that expels the bulk commodity payload from the open rear gate of the cargo-retaining space without any tipping of the trailer body. Still other trailer bodies are defines as “tipper” trailers, where the trailer body and chassis are supported on a platform and inclined as a unit so that the bulk commodity payload spills through the open rear gate.
While a variety of metallic materials have been employed to construct these trailer bodies, lightweight and high-strength metals, such as aluminum and various alloys thereof (referred to herein simply as “aluminum”, have become favored manufacturing stock because of the high strength-to-weight ratio, which allows for lower empty weight and optimum payload capacity, and also because of ease of manufacture and maintenance.
Another main advantage to use of aluminum in trailer and trailer body manufacturing is its resistance to corrosion. New ice and snow control techniques including use of liquid ice and snow melting compounds comprising magnesium chloride and/or calcium chloride have exacerbated the corrosion of conventional trailers having steel components in the chassis and/or trailer body. Liquid magnesium chloride and other compounds used for ice/snow control are many times more corrosive to steel as compared to “road salt” as we know it, e.g., sodium chloride. Also, these liquid ice/snow control compounds appear to act as a catalyst to the damaging electrolysis/galvanic reaction between steel and aluminum trailer components. These new ice and snow control techniques are becoming more popular due to a cost advantage and are causing extensive damage to steel components of truck trailers. This phenomenon is documented in the article “Corrosion Explosion” appearing in the September 2004 issue of Trailer/Body Builders, pps. 38–45. Because use of these new ice/snow control compounds is increasing, construction of durable, corrosion resistant aluminum trailers and trailer bodies is becoming increasingly popular and important.
To insure proper functionality, the interior sidewalls of a trailer body must be smooth to allow the payload to be dumped. Traditionally, trailer body sidewalls were defined using plates or rolled metal sheets, with any required support members being externally located to allow the cargo-retaining space to have the required smooth inward-facing walls. The external support members, and the sheet sidewall extending therebetween, caused the sidewalls to have an undulating exterior surface which has been found to increase wind drag and fuel consumption while also having a negative impact on handling in windy conditions.
More recently, to reduce wind-drag, the sidewalls of trailer bodies have been constructed using multiple interconnected extruded panels having smooth internal and external surfaces. Some of these trailer bodies include sidewalls that are defined by a plurality of extruded aluminum panels that extend length-wise the entire length of the trailer body, from the front wall to the rear wall. The long uninterrupted horizontal length of these panels, e.g., 48 feet or more, has led to problems in durability and strength. In particular, trailer body sidewalls constructed from a stacked plurality of horizontally extended panels are susceptible to weakness and, thus, outward bowing near the axial midpoint of the trailer body. Bowed sidewalls are highly undesired and are aesthetically displeasing and cause reduced confidence in the strength of the trailer body.
The floors of trailer bodies are constructed using plates or sheets of steel or aluminum or other material supported on a plurality of cross-members arranged transverse to the longitudinal axis of the trailer and spaced and intervals along the length of the trailer body. The cross-members are typically 3–5 inches high and remain exposed on the external underside of the trailer. As such, these cross-members and the floor supported thereon define an undulating exterior surface that with deep pockets between the cross-members. This exterior floor surface increases wind drag, collects dirt, ice/snow, corrosive ice/snow removal materials (e.g., sodium chloride, calcium chloride, magnesium chloride), asphaltic paving materials and other foreign matter. In the case of accumulated ice and snow, the collected material often hangs from the cross-members and further increases wind drag. The wind drag and accumulation of foreign matter are both highly undesirable conditions in that they increase weight, fuel consumption and/or negatively impact handling. Also, accumulated foreign matter can become dislodged during movement of the trailer on roadways which is undesirable for vehicles following the trailer.